Process and appliance for the production of gaseous products by decomposition of liquids

ABSTRACT

A continuous process for the production of a gaseous product (12), and as a liquid byproduct (16), at the same time by reacting a liquid reagent in a reactor (4) is disclosed. The positive difference between the pressure at the entrance to and an pressure at the outlet of the reactor (4) is kept constant. The process can be used to generate oxygen by decomposition of hydrogen peroxide and this oxygen can be used in welding and cutting sets.

This is a division of application Ser. No. 624,703 filed June 26, 1984now U.S. Pat. No. 4,601,884.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for the production of gaseousproducts by decomposition of liquids. It relates more particularly to aprocess for the production of oxygen by decomposition of hydrogenperoxide. It also relates to an appliance for implementing said process.

2. Background of the Art

The utilisation of gaseous oxygen usually requires the use of storagetanks that must be kept under pressure, which entails relativelycomplicated, expensive and cumbersome equipment. These drawbacks aresometimes prohibitive. This is the case when oxygen is destined to beused as an oxidising agent in portable welding or cutting sets.

Consequently, it was proposed in European Patent Application EP-A-No. 0007 118 filed on 18th April 1979 in the name of B.B.R. Instruments thatoxygen be generated by catalytic decomposition of hydrogen peroxide in aparticular appliance. This appliance, although very effective, hascertain disadvantages. For example, the flow of oxygen and theefficiency decrease gradually over time and the performance of theappliance varies considerably depending on the origin of the hydrogenperoxide solution used. Moreover, the heat released by the decompositionof hydrogen peroxide is expelled with difficulty and the oxygen formedcontains appreciable quantities of water vapour which is detrimental tothe stability and the temperature of the torch flame. Finally, thedesign of the appliance involves maintaining a not inconsiderable deadvolume of aqueous peroxide solution in the storage tank.

SUMMARY OF THE INVENTION

This invention relates to a continuous process for the production of agaseous product by reaction of a liquid reagent. The liquid reagent isintroduced continuously into a reactor in order to obtain a gaseousproduct and a light product. The process is conducted so as to maintainthe positive difference between the pressure at the entrance to thereactor and the pressure at the outlet of the reactor constant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate sideview cross-sections of the apparatusaccording to the invention.

FIGS. 3 and 4 illustrate a sideview and cut-away end view of thereaction zone, vertical conduit and gas collection zone reactorconfiguration, which aids in the separation of the gaseous product fromliquid medium.

FIG. 5 is an isometric view of the exterior showing the reactorconnected to an upper horizontal vessel through a conduit having coolingvanes mounted thereon.

FIGS. 6 and 7 illustrate sideviews of embodiments of the apparatus thatinclude tanks to contain pressurized gaseous fuel.

The present invention aims to provide a process and an appliance forgenerating a gaseous product such as oxygen by decomposition of a liquidsuch as hydrogen peroxide which do not have the disadvantages of theknown processes and appliances. For example, the process according tothe invention thus enables gaseous oxygen to be generated in anapproximately constant flow without catalyst deactivation being observedand without the process being dependent upon the quality of the hydrogenperoxide solution. It also enables gaseous oxygen to be obtained at asufficient pressure for it to be utilised notably as an oxidising agentin a welding set. Finally, the process according to the invention can,if necessary, be used without recourse to another external source ofenergy.

The appliance used to carry out the process according to the inventioncan be self-contained and portable. It can, if necessary, have verysmall external dimensions and thus be easy to handle. Moreover, its usedoes not involve any risk. If the apppliance according to the inventionis used to generate oxygen destined to be employed as an oxidising agentin welding sets, very hot and very stable flames are obtained.

To this end, the present invention relates to a continuous process forobtaining a gaseous product by reaction of a liquid reagent according towhich the liquid reagent is introduced continuously into a reactor inorder to obtain a gaseous product and a liquid product and in which thepositive difference between the pressure at the entrance to the reactorand the pressure at the outlet of the reactor is kept constant.

The process according to the invention is particularly advantageous whenthe reaction requires the use of solid particles at the reactiontemperature, serving for example as a reagent or catalyst, which areplaced in the reactor. Good results have been obtained when the reactorcontains solid particles of catalyst.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term liquid reagent is intended to mean a reagent or a mixture ofreagents which are themselves liquid or which are in the form of asolution in at least one suitable solvent at the temperature at whichthey enter the reactor. Generally, the term is intended to mean reagentswhich are liquid or in the form of a solution at ambient temperature. Ifthe liquid reagent is in the form of a solution in a solvent, thesolvent is chosen from those that are inert with respect to the reactionand which are capable of dissolving at least 5% and preferably at least10% of their weight of reagents. Good results have been obtained withliquid reagents in the form of a solution in a solvent. Generally, asolvent which dissolves less than 10% of the gaseous product at ambienttemperature is chosen. An example of a suitable solvent is water.

The term gaseous product is intended to means a product or a mixture ofproducts which are gaseous at ambient temperature and which are formedby reaction of liquid reagents.

The term liquid product is intended to mean a product or a mixture ofproducts which are in liquid form at ambient temperature. It may be aproduct formed by the reaction which is itself liquid, a liquid solventor a solution in at least one solvent in which the product formed by thereaction and possibly the unconverted reagent are dissolved.

The term positive difference between the pressure at the entrance to thereactor and the pressure at the outlet of the reactor is intended tomean the difference in pressure that is present when the levels of theliquid reagent at the entrance to the reactor and of the liquid productat the outlet of the reactor are the same, that is, in the case of areactor placed in a horizontal position. If these levels at the entranceand the outlet are different, this pressure difference is corrected by avalue equal to the pressure corresponding to the weight of a column ofliquid reagent the height of which is equal to the difference in levelbetween the entrance of the liquid reagent and the outlet of the liquidproduct, this correction being positive when the entrance of the liquidreagent is at a lower level than that of the outlet of the liquidproduce, and negative when the converse is true.

The difference in pressure between the entrance and the outlet of thereactor, provided that it is constant throughout the period when theprocess according to the invention is being carried out, cannevertheless be adjusted to different values depending on the nature andcomposition of the liquid reagents, the reactors used (shape, filling,pressure drop etc) and depending on the shape and dimensions of thesolid bodies such as catalysts that may be placed in the reactor.

Generally, in the case of a reactor placed in a horizontal position, thedifference in pressure between the entrance and the outlet of thereactor is at least 0.0001 MPa and preferably at least 0.003 MPa. It canhave much higher values but, from a practical point of view, it does notgenerally exceed 0.05 MPa and preferably 0.01 MPa. Generally, care istaken to ensure that the difference in pressure varies by less than 20%and preferably by less than 10% during operation.

The pressure of the gases produced by the process according to theinvention can be variable. The absolute pressure is generally at least0.1001 MPa and most often at least 0.101 MPa. Generally, for practicalreasons, it does not exceed 1 MPa and preferably 0.6 MPa. Of course,these values depend conventionally on the flows of liquid reagent passedto the reactor and on the size of the reactor.

Various methods can be used to keep the difference in pressure betweenthe entrance and the outlet of the reactor constant. For example, it ispossible to use an intermediate constant level tank to feed the liquidreagent. This tank is placed in such a way that the level of the liquidreagent is situated at a higher level than that of the entrance to thereactor and the top of this tank is brought into contact with thegaseous phase collected at the outlet of the reactor. In this case, thedifference in pressure between the entrance and the outlet of thereactor is ensured by the weight of the column of liquid reagent in theintermediate tank.

This very simple method is particularly advantageous because it obviatesthe need for external sources of energy.

A constant difference in pressure between the entrance and the outlet ofthe reactor can also be ensured with the aid of a pump with which it ispossible to regulate the operating pressure. In this case, the pressureat the outlet of the reactor is measured with a pressure gauge and thepressure at the entrance to the reactor is regulated accordingly withthe aid of the pump. An adjustment of this kind can be made manually orautomatically by any method known in itself.

Various types of reactors can be used to carry out the reaction. It ispreferable to use reactors in which the liquid reagent flowshorizontally. It is thus possible to use one or more tubular reactorsplaced horizontally in which the solid particles involved in thereaction can be placed. If the solid particles are consumed or graduallydeactivated by the reaction, it is advantageous to place them incartridges the walls of which are provided with openings so as to allowthe liquid reagent to flow through the cartridge. If the solid particlesare consumed or deactivated, these cartridges are simply replaced.

It is possible to use conpletely or partially submerged reactors. It isadvantageous to provide, in the upper part of the reactor, a zone whichis not submerged, which does not contain any solid particles involved inthe reaction and in which the gaseous product can be released.

This technique allows the gaseous product to be removed as it is formedby the reaction. A technique such as this has numerous advantages. Itallows the conversion rate to be increased because one of the productsof the reaction leaves the reaction medium and because contact betweenthe liquid reagent and the solid particles is better when the gaseousproduct formed is removed.

Moreover, as the reaction simultaneously generates a gaseous produce anda liquid product, the two products formed are thus separated immediatelyand can, if necessary, be collected in separate places.

Moreover, if the reaction is exothermic, the non-submerged zone of thereactor can be provided with heat exchange apparatus to prevent theliquid product formed evaporating completely and to control thetemperature of the gaseous product formed.

Depending on the type of reactor used, it is therefore possible tocollect either a mixture of gaseous and liquid products which can takethe form of a single gaseous phase if its temperature is sufficientlyhigh or the form of a mixture of vapours and liquids, or to collectseparately a gaseous phase comprising essentially the gaseous productand a liquid phase comprising essentially the liquid product.

If the reaction is exothermic, it is important to provide a system forremoving effective heat. If necessary, the products collected at theoutlet of the reactor can be passed to a condensation zone or a coolingzone. These generally comprise at least one heat exchanger and at leastone liquid separator. It is possible to use various types of heatexchangers known in themselves and comprising heat exchange surfaces ofall types such as plates, coils etc. It is also possible to useexchangers with one or more stages. The reaction products canadvantageously be passed to one or more tubes of small cross-section andlong length and possibly fitted with plates, blades etc to improve heatexchange which are cooled by simple contact with the surrounding air.Various items of equipment known in themselves can be used as liquidseparators, such as droplet removers.

The process according to the invention can be used to carry out variousreactions in which a liquid reagent is used to obtain a gaseous productand a liquid product. It is particularly suitable for obtaining oxygenby catalytic decomposition of hydrogen peroxide. In this case, anaqueous solution of hydrogen peroxide is introduced into a reactorcontaining solid particles of a hydrogen peroxide decomposition catalystin order to form a mixture containing oxygen and water vapour, themixture thus obtained is cooled in a condensation zone so as to form agaseous phase containing essentially oxygen and a liquid phasecontaining essentially water which is removed and the positivedifference between the pressure of the aqueous solution of hydrogenperoxide at the entrance to the reactor and the pressure of the gaseousphase containing essentially oxygen in the condensation zone at theoutlet of the reactor is kept constant.

The oxygen formed in the process according to the invention is generallypurified before being used. To this end, the mixture collected at theoutlet of the reactor is cooled in a condensation zone so as to removethe water formed by the reaction. This mixture is thus passed to a heatexchanger and a water separator.

If the reactor is small in size and the oxygen flows are not too high,the mixture emerging from the reactor can be passed to a vessel equippedwith a draining cock which will act both as a heat exchanger and a waterseparator. This vessel is generally situated at the same level as or ata lower level than that of the reactor such that the condensed water canbe removed by gravity. Most often, this vessel is situated beneath thereactor. An additional heat exchanger is often placed on the oxygenoutlet pipe in order to remove the final traces of water vapourentrained by the oxygen. The use of an additional heat exchanger isparticularly useful if the oxygen is destined to feed a welding setbecause it prevents formation of water droplets which would be flunginto the torch flame.

The aqueous solutions of hydrogen peroxide used can have variableconcentrations. Generally, solutions containing 10 to 75% and most often15 to 65% by weight hydrogen peroxide are used. Good results areobtained with concentrated commercial solutions which generally containapproximately 35% by weight hydrogen peroxide. The solutions of hydrogenperoxide can, if necessary, contain various customary additives. Theycan for example contain stabilisers known in themselves such asphosphoric or phosphonic acid and their derivatives such as their saltsand more particularly sodium pyrophosphate or acid sodium pyrophosphate.They can also contain corrosion inhibitors and passivating agents knownin themselves such as ammonium nitrate or sodium stannate. They can alsocontain anti-foaming agents.

To effect the decomposition of hydrogen peroxide to water and oxygenvarious types of catalysts known for this purpose can be used. It isthus possible to use elements of periods 4, 5 and 6 of groups 1b, 2b,4a, 5a, 6a and b, 7a and b, and 8 of the International Classification ofthe elements and their derivatives. Good results have been obtained withcatalysts based on metals such as gold, silver, platinum, palladium,manganese, iron, chromium, copper, cobalt and lead and their derivatessuch as their oxides and their salts. Advantageous results have beenobtained with catalysts based on lead, platinum or palladium and theirderivatives. Platinum has given excellent results. Other catalysts knownin themselves can also be used and it is possible to use mixtures ofdifferent catalysts.

The catalysts can be placed as such in the reactor or they can be placedon suitable supports known in themselves. They can be deposited on thesupports either physically or chemically. Various supports can be used.It is thus possible to use supports chosen from silicas, aluminas,alumino-silicates, activated charcoal, pumice stone, zeolites,bentonites, carborundum, diatomaceous earths, fullers earth and porousmetal supports. Supports with good heat resistance and good mechanicalresistance which do not undergo attrition and which do not shatter dueto the effect of the pressure generated by the formation of the gaseousproduct in the pores of the support are generally chosen. The supportsmust also be chemically resistant to the reagents used and the productsformed.

Goods results have been obtained with supports chosen from the aluminas,silicas and alumino-silicates.

Platinum deposited on alumina in a quantity of 1% of its weight hasgiven excellent results during the decomposition of hydrogen peroxide.

The catalyst particles can take various forms. It is thus possible touse bars, tablets, extrudates, granules or spheres. Generally, in orderto avoid pressure drops, particles more than 0.05 cm in size and mostoften more than 0.1 cm in size are used. Generally, their greatest sizedoes not exceed 20 cm without this limit being critical.

If the process according to the invention is applied to the productionof oxygen by decomposition of hydrogen peroxide, the various parts ofthe appliance used for this purpose which are in contact with hydrogenperoxide, possibly in the form of traces, are made advantageously out ofmaterials which are resistant to corrosion by hydrogen peroxide.Aluminium, glass and certain polymers such as polypropylene,polytetrafluoroethylene, polyethylene, poly-1,1-difluoroethylene etc aresuitable for this purpose.

The process according to the invention can be used to generate oxygensuitable for various uses. It can, for example, be used to generateoxygen for portable welding sets, to generate oxygen for inhalersenabling the air to be enriched with oxygen in variable quantitiesgenerally between 28 and 50% and most often Between 25 and 40% by weightoxygen and also to generate oxygen for fuel cells.

The invention also relates to a process for generating oxygen for theproduction of flames suitable for welding or cutting.

The invention also relates to appliances suitable for the production ofgaseous products according to the process of the invention andcomprising a device for keeping constant the positive difference betweenthe pressure at the entrance to the reactor and the pressure at theoutlet of the reactor.

In a self-contained appliance, a storage tank for the liquid reagentplaced at a high level feeds an intermediate tank with a constant level;the latter feeds a reactor placed in a horizontal position and packedwith solid particles by means of a line comprising an adjustable flowvalve and a non-return valve for the contents of the reactor; thereactor is situated at a level below the constant level of theintermediate tank; a line links the outlet of the reactor to a vesselcomprising a means of discharge; two lines connect the top of the vesselrespectively with the top of the intermediate tank by a pressureequalising pipe comprising a non-return valve for the contents of theintermediate tank and with a heat exchanger which is itself linked tothe outlet of the appliance.

In another appliance, a storage tank for the liquid reagent feeds, bymeans of a line comprising an adjustable pressure pump, a reactor placedin a horizontal position and packed with solid particles; a line linksthe outlet of the reactor to a vessel comprising a means of discharge;two lines connect the top of the vessel respectively to a pressure gaugewhich enables the adjustable pressure pump to be regulated, and to aheat exchanger which is itself connected to the outlet of the appliance.

The vessel comprising a means of discharge such as a cock can besituated at different levels. Generally it is situated at a level equalto or lower than and preferably lower than that of the reactor.

The process according to the invention can advantageously be carried outin sets of equipment such as those represented in FIGS. 1 and 2 whichrepresent different ways of carrying out the process according to theinvention.

FIG. 1 represents an appliance suitable for the production of a gaseousproduct by catalytic decomposition of a liquid reagent which comprises asmall intermediate feed tank 3 with a constant level fed by storagetank 1. A safety valve 2 is placed in the storage tank. Reactor 4 inwhich the decomposition catalyst is placed is fed with liquid reagent bymeans of an adjustable flow valve 5. A non-return valve 6 placed betweenthe reactor and the regulating valve prevents the pressure generated inthe reactor from forcing the liquid reagent back upstream. The liquidproduct formed by the decomposition reaction of the liquid reagent iscollected in vessel 7. A draining cock 16 enables the liquid product tobe drawn off. The gaseous product formed by decomposition of the liquidreagent passes to a heat exchanger 8 in which the liquid productentrained by the gaseous product is condensed. A grille 10 protects theheat exchanger. The gaseous product passes to an insulated line 18 andleaves at 12. The pressure between the outlet of the reactor and the topof intermediate feed tank 3 is equalised by means of line 17. Anon-return valve 22 separates line 17 from the intermediate feed tank 3in order to prevent the liquid reagent passing from tank 3 to line 17. Agauge 11 enables the pressure to be regulated. The appliance is placedin a case 15 with a handle 14. FIG. 1 also shows the reactor inlet zone35, the reactor outlet zone 36, and the hollow conduit 37 connecting thetop of vessel 7 with the heat exchanger 8 and the apparatus outlet 12.

The method of carrying out the process represented in FIG. 1 isparticularly advantageous because it does not require any externalsource of energy and is thus completely self-contained.

In the appliance shown in FIG. 2, the feed by means of an intermediateconstant level tank of FIG. 1 has been replaced by an adjustablepressure pump 19 which enables the pressure to be adjusted by means ofpressure switch 20. Storage tank 1 is vented at 21. FIG. 2 also showsthe hollow conduit 38 connecting adjustable pump 19 at its suction endto storage tank 1, and at its discharge end through reactor inlet zone35, to reactor 4. In addition, the pressure measuring device 11 is shownas being connected by a hollow conduit 39 to the upper part of vessel 7.

The sets of equipment represented in FIGS. 1 and 2 can also be used tocause a liquid reagent to react with particles of solid reagent. In thiscase, the particles of solid reagent are placed in reactor 4.

The process according to the invention can advantageously be carried outin reactors such as those represented in FIGS. 3 to 5.

FIG. 3 represents a sectional view of a reactor. The liquid reagententers via line 32 into reaction zone 34 where the solid partciles ofcatalyst or of reagent are placed. The gaseous product is liberated viavertical tubes 24 placed in the upper part of the reaction zone. Thegaseous product is collected in horizontal pipe 26 and caught in 27.Necks 28 are provided for at the bottom of the vertical pipes to preventthe solid particles of catalyst or reagent being entrained in saidpipes. The liquid product leaves the reactor at 23. Spaces 25 betweenthe pipes ensure heat exchange.

FIG. 4 represents a side view in section along the plane AA' of FIG. 3.

FIG. 5 represents a perspective view of another reactor. The liquidreagent enters via line 32 into reaction zone 34 where the solidpartciles of catalyst or reagent are placed. The gaseous product isreleased via the horizontal slit 31 placed in the upper part of thereaction zone and passes through chamber 33 acting as a heat exchangerand closed at the ends by walls 29. The side walls of this exchanger areprovided with blades 30. The gaseous product is collected in horizontalpipe 26 and caught in 27.

If the process according to the invention is used to generate oxygen forwelding sets, it is possible to use sets of equipment such as thoseshown in FIGS. 6 and 7 which represent different ways of constructing aportable supply set for welding by means of an oxygen/combustible gasflame.

FIG. 6 represents a supply set in which oxygen is generated according tothe scheme shown in FIG. 1. In this appliance, the combustible gasoriginates from cylinder 9 and leaves at 13. This supply set isparticularly advantageous because it is completely self-contained.

FIG. 7 represents a similar supply set in which oxygen is generatedaccording to the scheme shown in FIG. 2.

In order to illustrate the invention, some examples of carrying out theprocess according to the invention (examples 2 to 4) and a comparativeexample (example 1) are given below.

EXAMPLE 1

The test was carried out in a small commercial appliance very similar tothe one described in FIGS. 2 and 3 of European Patent ApplicationEP-A-No. 0 007 118 mentioned above except that the top of the storagetank for the aqueous solution of hydrogen peroxide was not connected tothe bottle of liquified gas (butane) 9 but to the outlet of the gaseousoxygen via line 12.

A commercial aqueous solution of 35% hydrogen peroxide was used. Thereactor made of aluminium had a volume of approx. 40 cm³ and contained,as a catalyst, 150 g of milled lead bars (Pb content 99.5%) 13 to 15 cmin length, 3 mm wide and 1 mm thick.

The aqueous solution of hydrogen peroxide was introduced into thereactor continuously for 45 minutes and the flow rate of oxygen producedwas measured over time. After 5 minutes' operation, this flow rate was240 1.h⁻¹ whereas after 45 minutes it had to fallen 150 1.h⁻¹ which isnot enough to produce a flame sufficiently hot for welding, the minimumflow to provide a flame with a satisfactory temperature being 180 1.h⁻¹.

EXAMPLE 2

The test was carried out in an appliance such as the one shown inFIG. 1. The constant level of the intermediate tank (3) was situated 25cm from the level of the entrance to the reactor.

The same aqueous solution of hydrogen peroxide as in example 1 was used.The reactor (4) with a volume of about 40 cm³ contained, as a catalyst,150 g of milled lead bars such as those used in example 1.

The aqueous solution of hydrogen peroxide was introduced continuouslyinto the reactor (4) for 24 minutes and the flow of oxygen produced wasmeasured over time. After 7 minutes' operation, this flow rate was 3601.h⁻¹. After 24 minutes it was 360 1.h⁻¹. There was therefore noappreciable change in the flow rate over time.

EXAMPLE 3

The test was carried out in an appliance such as the one shown in FIG.2. A MASTERFLEX pump (19) providing a pressure of 180 mm Hg was used.

The same aqueous solution of hydrogen peroxide as in examples 1 and 2,the same reactor (4) and the same catalyst were used.

The aqueous solution of hydrogen peroxide was introduced continuouslyinto the reactor (4) for 25 minutes and the flow of oxygen produced wasmeasured over time. The difference in pressure between the entrance andthe outlet of the reactor was kept at 8.10⁻⁴ MPa. After 5 minutes'operation, this flow rate was 250 1.h⁻¹. After 25 minutes, it was 2251.h⁻¹. There was therefore no appreciable change in the flow rate overtime.

A slight colouring of the waste water removed at (16) was observed overtime.

EXAMPLE 4

The same appliance as in example 3 and similar operating conditions wereused. Only the catalyst was replaced by granules of alumina impregnatedwith 1% platinum. These granules which take the form of spheres with amean diameter of 7 mm are sold by Johnson Matthey and Co. Ltd.

After 5 minutes' operation, the flow rate of oxygen was 240 1.h⁻¹ andafter 25 minutes it was still 240 1.h⁻¹. There was therefore noappreciable change in the flow rate over time.

The waste water did not contain any catalytic residue.

We claim:
 1. A continuous process for the production of a gaseousproduct by reaction of a liquid reagent, the processcomprising:introducing the liquid reagent continuously into a reactorhaving an inlet and an outlet in order to obtain a gaseous product and aliquid product, wherein a positive difference exists between thepressure at the inlet to the reactor and the pressure at the outlet ofthe reactor, which positive difference is kept constant.
 2. A processaccording to claim 1, wherein the reactor contains solid particles ofcatalyst.
 3. A process according to claim 1, wherein the difference inpressure ranges from 0.0001 to 0.01 MPa.
 4. The process according toclaim 1 applied to the production of oxygen by catalytic decompositionof hydrogen peroxide,wherein the liquid reagent is an aqueous solutionof hydrogen peroxide, the reactor contains a decomposition catalyst forhydrogen peroxide having the form of solid particles, and wherein thegaseous product is a gaseous mixture containing oxygen and water, andthe process comprises the further steps ofcooling the gaseous mixture ina condensation zone to form a gaseous phase consisting essentially ofoxygen and a liquid phase comprising water; and removing the liquidphase, wherein the positive difference between the pressure of theaqueous solution of hydrogen peroxide at the inlet to the reactor andthe pressure of the gaseous phase consisting essentially of oxygen inthe condensation zone at the outlet of the reactor is kept constant. 5.A process according to claim 4, wherein an aqueous solution containingfrom 15 to 65% by weight hydrogen peroxide is used.
 6. A processaccording to claim 4, wherein the solid particles of catalyst contain acatalytic element chosen from among lead, platinum and palladium.
 7. Aprocess according to claim 6, wherein the catalyst is composed ofplatinum on an alumina support.
 8. A process according to claim 2,wherein the reactor comprises in its upper part a zone which is notsubmerged and is free from catalyst.
 9. A continuous process for theproduction of a gaseous product by reaction of a liquid reagent, theprocess comprising:introducing the liquid reagent from a storage tankcontinuously into a horizontal reactor having an inlet and an outlet inorder to obtain a gaseous product and a liquid product, wherein thestorage tank is positioned above the horizontal reactor and a positivedifference exists between the pressure at the inlet to the reactor andthe pressure at the outlet of the reactor, which positive difference iskept constant.
 10. The process according to claim 9, wherein thehorizontal reactor contains solid particles of catalyst.
 11. The processaccording to claim 10, wherein the horizontal reactor comprises in itsupper part a zone which is not submerged and is free from catalyst. 12.The process according to claim 9, wherein the difference in pressureranges from 0.0001 to 0.01 MPa.
 13. The process according to claim 9applied to the production of oxygen by catalytic decomposition ofhydrogen peroxide, wherein the liquid reagent is an aqueous solution ofhydrogen peroxide, the horizontal reactor contains a decompositioncatalyst for hydrogen peroxide having the form of solid particles, andthe gaseous product is a gaseous mixture containing oxygen and water,and the process comprises the further steps ofcooling the gaseousmixture in a condensation zone to form a gaseous phase consistingessentially of oxygen and a liquid phase comprising water; and removingthe liquid phase, wherein the positive difference between the pressureof the aqueous solution of hydrogen peroxide at the entrance to thehorizontal reactor and the pressure of the gaseous phase consistingessentially of oxygen in the condensation zone at the outlet of thehorizontal reactor is kept constant.
 14. The process according to claim12, wherein an aqueous solution containing from 15 to 65% by weighthydrogen peroxide is used.
 15. The process according to claim 12,wherein the solid particles of catalyst contain a catalytic elementchosen from among lead, platinum and palladium.
 16. The processaccording to claim 15, wherein the catalyst is composed of platinum onan alumina support.